docs: def set(self, start, stop, length=None, units='bytes'):
          """Simple method to update the ranges."""
          assert is_byte_range_valid(start, stop, length), \
              'Bad range provided'
          self._units = units
          self._start = start
          self._stop = stop
          self._length = length
          if self.on_update is not None:
              self.on_update(self)